A novel offset compensation biquad switched-capacitor filter design

Based on the architecture of traditional biquad switch-capacitor (SC) filter, placing a low-frequency zero in the transfer function of the filter by the method of adding a SC integral in the feedback path of the circuit, we designed a novel biquad SC filter used in the RFID reader. The new architecture can compensate the DC offset comes from the input and the internal offset originated by the mismatch within the differential circuit of the filter. And the output offset of our design is determined by the input offset of the integrator in the feedback path. The result of simulation show the output offset of this new architecture can be controlled within 30 mv if the input offset change from 50 mv to 500 mv.